US1822247A - Box-shaped central portion of metal aircraft wing - Google Patents

Description

L. STAIGER Sept. 8, 1931.

BOX SHAPED CENTRAL PORTION OF METAL AIRCRAFT WING Filed April 25, 1927 Patented Sept. 8, 1931 PATENT OFFICE LUD'WIG STAIGER, OF SPANDAU, NEAR BERLIN, GERMANY, ASSIGNOR TO THE FIRM:

' ROHRBACH METALL-FLUGZEUGBAU, G. M. B. 3., OF BERLIN, GERMANY BOX-SHAPED bENTRAL PORTION OF METAL AIRCRAFT WING Application flied April 25, 1927, Serial Rb. 186,224. and in Germany Kay 4, 1926.

Metal aircraft wings tri-partite in the direction of flight and including a box-shaped central portion with re-inforced base, are well known in the art. The flush outer skin of said central portion, attached to the griders of the interconnected longitudinal webs and transverse ties are re-inforced, in the panels between thc girders, by riveted on profiles arranged parallel to the longitudinal webs along the inner surfaces of the skin and passing through lightening holes in girders of the transverse ties, the profiles being of their girders. This new feature has the advantage of avoiding any reduction of strength in the girders of the transverse ties, which, therefore, can be economically manufactured at and receive a more efiicient shape. \Vith this form of construction one succeeds in completely avoiding the hitherto prevailing inconveniences and difficulties in the assembly of profiles and transverse ties. resulting in considerable saving of time. Instead of the elongated profiles, which are being expensive in manufacture and of bulky structure, cheaper and more handy sections can be used. Moreover from a statical point of View this form of construction has many marked advantages. The re-inforcing profiles arranged in the direction of flight efficiently protect the box-angles against bending and torsion stresses, at the same time supporting the longitudinal webs, to the girders of which they are attached.

The structure of the box can be considerably simplified by arranging the re-inforcing webs of one-skin, and preferably of the bottom skin, at the outside of this skin. The box can then be assembled, after having covered the frame work of longitudinal webs and transverse ties with the top skin, by riveting the inner profiles to the top skin and /or the girders of the longitudinal webs, afterwards attaching the bottom skin,

which may have already been provided with profiles on its outside. In all cases the rivet seams can be made without any difliculty, as the box permits of easy access from the bottom side, thus facilitating work at the top skin, whereas the outside arranged webs profiles of the bottom skin onl necessitate the driving in of rivets arrange at the girders of the longitudinal webs.

In the drawings is shown, by way of example, a form embodying construction of the subject matter of the present invention.

Fig. 1 shows the box-shaped central portion, in side elevation.

Fig. 2 is a section on the line AB of Fig. 1.

Fig. 3 represents longitudinal web in plan view which has not yet been covered with a skin.

Fig. 4 is a section on the line CD of Fig. 1 on an enlarged scale.

Fig. 5 is a section on the line EF of Fig. 4. Fig. 6 shows part of the bottom skin of the Win Fig. 7 represents a transverse tie.

Fig. 8 is a detailed part, shown in perspective.

The boa-shaped central portion, to which leadingand trailing edges are hingedly attached and which impart the final sectional form to the wing, consists of two lateral longitudinal webs a, interconnected b transverse ties arranged at intervals. he web elements are in skeleton form and they as well as transverse ties are provided with girders or angled elements or bars 6, d, to which the flush topand bottom skins e, f, are attached, forming a hollow body comprising longitudinal spars, cross connections and skins or covers of eiiicient bending and torsional strength.

The well known practice of re-inforcing the skin panels between the girders d, 0, 1s improved, according to this invention, by using profiles g, h, running parallel to the transverse ties b and attached to the Web girders a, and of which the former are of C- shaped section and riveted on the inside of the top skin e, whereas the latter, havingan A-shaped section, are arranged on the outside of the bottom skin of the wing. The profiles h, of streamlined section, are provided with a sufiiciently large riveting border even at their frontal ends, and are pressed or the like into the section shown in such manner, that the end parts of the pressed parts, completely covering up the profile opening, gradually merge into the end-borders, to which the web girders are riveted.

Assembly of the central portion is as follows: top skin 6 being riveted on the framework of longitudinal webs a and transverse ties b, the profiles g are attached to the inside of the skin and the girders c, which presents no difficulty, as all places where rivets must be made, are easily accessible owing to the missing bottom skin. Then the bottom skin f, having already been provided with outside profiles h, is attached, so that only the riveting thereof to the fully accessible girders 0 remains. This new manner of arranging the profiles most perfectly retains the convex form of the skin, since all deformations are limited to the small length between any two re-inforcing profiles.

Special reasons, as for instance, obtaining a top skin which may be walked upon safely, may result in arranging the profiles h, in contradistinction to the described manner, on the top skin, and the profiles g on the inner side of the bottom skin. It is clear that top skin as well as bottom skin may be provided without outside profiles h.

A practice comparing favourably with those hitherto adopted, provides open profiles and the represented C-profile preferably, on the inside of both skins. An open structure is thereby obtained, such as all seaplane constructors aspire to obtain, with a view to facilitate inspection and thus avoiding corrosion. Compared with this most vital feature, the somewhat difiicult assembly of the box is absolutely without importance.

The transverse ties b, the efi'iciency of whose girders had been considerably impaired by the intermediate profiles of the prior practice, after the adoption of the new practice consist onl of simple thin plates, re-inforced b vertical bars 11, which plates preferably s ould be provided with lightening holes is and flanges m at the edges of the lightening holes. The girders d, continuous and unimpaired, may be formed by a flange n of the plate. In this case it is to be recommended to re-inforce said girders by an outside profile h (Fig. 5),'which particularly should be used, when local stresses are prevailing, occasioned for example by landing-gear attachments, engine nacelles etc.

It has proved of advantage to re-inforce the skin panels also in wing span direction, this being done, for instance, by means of metal bands or strips 0 arranged vertically on the inner side of the skin. Those bands or strips can be formed according to a well known practice, by flanges of overlapping skin connections p, holding together two or more skin runs arranged at a stretch in the direction of flight and extending in win span direction over several transverse ties If, for any reason, it does not seem desirable to flange the edge of some skin run, a section similar to that indicated in Fig. 2 may be riveted on the connecting seam. This bar 9 is used, when the skin is not provided with a scam in wing span direction, as represented in Fig. 2, to the left. The rc-inforcing memhere 0, g are arranged between the continuous re-inforcing profiles g, h, if both are attached to the same side of the skin, as shown in Fig. 2. Their effect is considerably increased if they extend continuously, and uninterruptedly cross the profiles arranged at the o positeside of the skin, as shown, by way 0 example, in the bottom skin according to Figs. 4 and 5. The resulting crossanember frame is of perfect strength and resistance.

The invention can be applied with equal advantage tohollow box girders with three or more longitudinal webs. It is of no consequence whether the connection of the remaining re-inforcing profiles, which ma be shaped according to requirements, wit the wing skin is effected by means of screwing, welding or thelikc, instead of riveting. 1n the same manner the invention could be applied to the lateral and horizontal control surfaces, as same consist of rudder and bipartite fin, the leading ed e of which latter is designed to be detachable.

What I claim is:

1. A metallic box girder wing structure for airplanes including spaced longitudinal spars of sufiicient depth to give the required wing thickness, and adapted substantially to solely transmit the vertical bending forces, cross ties rigidly bracing said spars, thin and smooth cover plates extending over several cross ties and lying fiat against and fastened rigidly and directly to both the s are and the cross ties to form a rigid part ta ring up tensile stresses of the box girder, the skin panels defined by the s are and cross ties being provided with, sti ening profiles extending to and lying transverse to the spars, and rigidly fixed to the cover plates, said profiles being adapted to transmit the compression force components of transverse forces from one longitudinal spar to the other.

2. A metallic box girder wing structure for airplanes including spaced longitudinal spars of sufiicient depth to give the required wing thickness, and adapted substantially to solely transmit the vertical bending force, cross ties rigidly bracing said spars, thin and smooth cover plates extending over several cross ties and lying fiat against and fastened rigidly and directly to both the spars and thecross ties to form a rigid part taking up tensile stresses of the box girder, and

the skin panels defined by the spars and cross ties being provided with stiffening profiles extending to and lying transverse to the spars, and rigidly fixed to the profiles, said panels being firmly connected at their ends to the spars, the cross reenforcing profiles being adapted to transmit the compression force components of transverse forces from one longitudinal girder into the other.

3. An aircraft wing including a box base, said box consisting of vertical spars, spaced from each other and rigidly connected and braced by cross ties which are also spaced from each other, the top and bottom of the box being covered by a thin and smooth skin which is rigidly connected with the spars and cross ties in a manner to participate in the transmission of compression force componcnts of the box base, the skin panels defined by the spars and the cross ties being provided with stiffening rofiles firmly fixed thereon, and extending in the direction of flight, said profiles being firmly connected at their ends to the spars, and adapted to transmit the compression force components of transverse forces from one longitudinal girder onto the other.

4. An aircraft wing including a boxshaped base and edge parts joined thereto, said edge parts completing the wing section, said box composed of longitudinal spars spaced from each other, cross ties connecting the spars and smooth upper and lower skin cover plates participating in the transmission of forces, the cross ties being spaced a certain distance from each other, the spars and cross ties having girder flanges attached thereto and the upper and lower skin plates being fixed to these flanges, said skin plates essentially transmitting only the compression force components of tnansvcrse forces, panels defined by the longitudinal spars and transverse ties profiles fixed on the skin panels and nnctioning to stiffen the stressed skin structure, said profiles extending transverse to the spars and being connected at their ends to the flanges of the spars, and arranged to transmit the compression force components of transverse forces from one longitudinal girder to the other.

5. In an aircraft wing, a hollow box girder constituting the central portion thereof, the box consisting of two lateral girders arran ed a distance from each other and inclu ing smooth upper and lower skin plates fixed to the lateral girders, said upper and lower skin forming a rigid part of the box and transmitting essentially solely the compression force components of transverse forces, cross ties arranged within the box a certain distance from each other and rigidly connected with both the lateral girders and the smooth skins, strengthening bars connected to the skins and extending from the front lateral bearer to the rear lateral bearer and being fixed to both bearers, said bars being adapted to transmit the compression force components of transverse forces from one lateral girder onto the other.

6. A hollow box girder constituting the base structure of an aircraft wing, the box including lateral spars and smooth upper and lower skin plates rigidly connected thereto. said upper and lower skin plates transmitting essentially solely the compression force components of transversely acting forces, cross ties arranged within the box a certain distance from each other, the cross ties being connected with the spars and the skins, stiffening bars rigidly connected to the skins, the bars being located in the direction of flight between the cross tics and being connected also with the spars, said bars being adapted to transmit the compression force components of transverse forces from one lateral spar to the other, the bars of one skin being located on the inner side of the skin, the bars of the other skin being located on the outer side of the skin.

7. A hollow box girder according to claim 6, wherein the stifi'cning bars of the upper skin are located on the inner side of the skin, the bars of the lower skin being located on the outer side of the skin.

8. A hollow box girder constituting the foundation of an aircraft wing, the box including lateral spars and smooth upper and lower skin plates rigidly connected thereto, said upper and lower skin plates transmitting essentially solely the compression force components of transverse action of the box, cross ties arranged within the box a certain distance from each other, the cross ties being rigidly connected with both the spars and the skins, stiffening bars fixed to the skins, the bars being located in the direction of flight between the cross ties and connected with the spars, two or more bars being located within the box space, said bars being adapted to transmit the compression force components of transverse forces from one lateral spar to the other, said bars consisting of sections which are free at one longitudinal edge after their fixation.

9. A hollow box girder according to claim 8, the open sections being C-shaped profiles with flanges or girders of unequal width, the larger one being against the skin.

10. A hollow box girder constituting the base structure of an aircraft wing, the box including lateral spars and upper and lower skin plates connected thereto. said upper and lower skin plates participating in the transmission of forces oi the box, cross ties arranged within the box a certain distance from each other, said cross ties be ng connected with both the spars and the skins, stiffening bars being fixed to the skins and located in the direction of flight between the cross ties and also connected with the spars, certain of the stiflening bars being located on the outer side of the box skins, said exterior bars consisting of a hollow section and havin their ends stream-lined and formed into lateral edges bent 011' the hollow section, said edges serving for fixing the sti fl'ening sections to the box wall.

11. A hollow box girder according to claim 10, wherein hollow profiles are also arranged in the plane of the cross ties.

12. A hollow box girder constituting the base structure of an aircraft wing, the box including lateral sp'ars and smooth upper and lower Skln plates connected thereto, said up-' per and lower skin plates participating in the transmission of forces of the box, cross ties arranged within the box a certain distance from each other, said cross ties being connected with the spars and the skins, stiffening bars fixed to the skins, the bars being located in the direction of flight between the cross ties andbeing connected with the spars, the skins being provided with connections which ruri in the direction of the wing span, the edge of the skin being bent round at a right angle at certain places of connection, said flan es being located on one side of the skin, t e stiffening bars which are fixed separately and run in the direction ,of flliight, being located on the other side of the s in.

13. A hollow box girder constituting the base structure of an aircraft wing, the box including lateral spars and upper and lower skin plates connected thereto, said upper and lower skin lates being smooth and participating in the transmission of forces of the box, cross ties arranged within the box seer-- tain distance from each other, said cross ties being connected with both the s arc and the skins, stiffening bars fixed to t e skins, the bars being located in the direction of flight between the cross ties and being connected with the spars, the longitudinal walls and cross ties forming skin anels, the skin anels at the wing end a jacent the fuse a being formed' by one sheet panel, the skin panels of the wing central portion being formed by two skins located one behind the o her in the direction of flight and each of them extending over several cross ties.

14. A hollow box girder according to claim 13 wherein the skin panels of the wing tip consist of three skins located one behind the other in the direction of flight and each of them extending over several cross ties.

15. A hollow box girder constituting the base structure of an aircraft wing, the box including lateral longrons and upper and lower skin plates connected thereto, said upper and lower skin plates being smooth and participating in the transmission of forces of the box, cross ties arranged within the box a certain distance from each other, said cross ties being connected with the spars and the skins, stifiening bars being fixed to the skin the bars being located in the direction 0 flight between the cross ties and being connected with the spars, certain of said cross ties consisting of a sheet panel with the upper and lower edge being reinforced by flanges, these sheet panels havin grooves with flanged edges, stiffening mem rs being fixed on the sheet panels, said stiffening members being substantially vertical and being connected with the flanges of the said top and bottom edge.

16. A box-shaped central portion of a metal aircraft win formed of three parts in the direction of flight, said central ortion including two lateral longitudinal we s, and consisting of cross walls which connect the longitudinal webs with each other and are arranged a certain distance fromeach other, and also including smooth upper and lower skin plates which are connected to the longitudinal webs and to the cross ties and articipates in the transmission of forces 0 the box, the upper and lower skin plates being provided with stifl'ening members, said members being located in the direction of fli ht between the cross ties and being connecte to the two longitudinal webs, the stiffening members of at least one of the skins being located on the inner side of the skin.

17. A box-shaped central ortion of a metal aircraft wing formed of t rec parts in the direction of flight; said central portidn including two lateral longitudinal webs, cross walls which connect the longitudinal webs with each other and are arranged a certain distance from each other, and smooth upper and lower skin plates which are connected to the longitudinal webs and to thecross ties and participate in the transmission of forces of the box, the u I per skin being provided on its inner side an the lower skin on its outer side with stifiening members, said members being lodated in the direction of flight between the cross ties and being connected to the two longitudinal webs.

18. A box-shaped central ortion according to claim 17, the inner sti ening members consisting of opexrC-shaped sections, the exterior stitfening members consisting of open sections with edges which ,are flanged all round, said edges serving for connecting the sections to the skin, the fixed sections forming with the skin closed profiles.

19. A box-shaped base structure according to claim 1, the wing being reinforced at the root.

20. A box-(girder construction for aircraft wings inclu i plates and reinforcing members extending in the fore and aft direction attached to said plates of A-section and having their ends stream-lined, with the marginal edges formed into securing flanges lying flat against the plates.

ng stressed metal covering- 21. A box-shaped central member for use between the front and rear members of a tripartite metal aircraft wing, having a smooth outer skin which is attached to the 5 girders of interconnected longitudinal webs and transverse ties and is reinforced, in the panels between the girder members, by means of'profile bars, the'reinforcing profile bars being parallel with the transverse ties and 10 having their ends attached to the longitudinal Webs of their girder members.

In testimony whereof, I have signed my name to this specification.

15 LUDWIG STAIGER.

21. A box-shaped central member for use between the front and rear members of a tripartite metal aircraft wing, having a smooth outer skin which is attached to the girders of interconnected longitudinal webs and transverse ties and is reinforced, in the panels between the girder members, b means of profile bars, the reinforcing pro le bars being parallel with the transverse ties and having their ends attached to the longitudinal webs of their girder members.

In testimony whereof, I have signed my name to this specification.

LUDWIG STAIGER.

CERTIFICATE OF CORRECTION.

Patent No. 1,822, 247. Granted September 8, 1931, to

LUDWIG STAIGER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 30, strike out the word "being"; page 2,- line 33, for "without" read with, and line 72, after "section" insert bar q; page 3, line 42, claim 4, before "panels" insert the word skin; page 5, line 11, claim 21, for "of" read or; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 27th day of October, A. D. 1931.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,822,247. Granted September 8, 1931, to

LUDWIG STAIGER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1. line 30, strike out the word "being"; page 2,' line 33, for "without" read with, and line 72, after "section" insert bar 1 page 3, line 42. claim 4, before "panels" insert the word skin; page 5, line 11, claim 21. for "of" read or; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 27th day of October, A. D. 1931. n

M. J. Moore. 1 (Seal) Acting Commissioner of Patents.

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